Add dashboard to admin page

Default home page: fix wiki link title; GitHub wiki is obsolete, because it has been moved from GitHub to independent resource.

closes #6212

Default home page: fix indent level; fix indentation level for configuration message block to make it looks like other blocks.

closes #6206, closes #6205

Fix profile visibility icon

closes #6183

Better display for stream faces

this is the suggested styling according to hound/pronto/rubocop
(#6192)

instead of before blocks creating instance variables
pronto checked

#6192

(#6192)

#6192

and dipatch is also called in the following test
#6192

instead of instance variables
(#6192)

since dispatch method is not private
(#6192)